Toyota is pushing hydrogen-powered vehicle technology forward with a liquid hydrogen system design that includes a self-pressurizer to save escaping gas and reuse it as fuel to increase engine efficiency.

Toyota introduced a liquid system in the GR Corolla H2 Concept in 2023, which keeps hydrogen at -253 degrees Celsius during filling and storing in the tank. Hydrogen exists as a gas at room temperature, so the pumps have to operate cold to prevent the liquid from boiling. Inherently, the system still has boil-off gas that gets wasted.

So what’s the solution? Toyota exhibited a “self-pressurizer” at the Super Taikyu Series 2024 race this past weekend that “uses the pressure of the boil-off gas to increase pressure by two to four times and produce reusable fuel without using any additional energy.” It then hopes to feed any additional boil-off to a small fuel cell package to power the hydrogen pump motor for further efficiency.

Liquid hydrogen vehicles are a much more technically grueling affair for both storage and system configuration. “Hydrogen pumps are the most failure prone components in all hydrogen systems — cryogenic or gaseous,” writes Washington State University professor Dr. Jacob Leachman in an email to The Verge. “What Toyota seems to have cleverly done is develop a hydrogen pump that harnesses part of the cold energy for compression purposes — an advance needed by anyone developing cold hydrogen vehicles.”

Leachman, who heads the university’s Hydrogen Properties For Energy Research (HYPER) Laboratory, said another challenge is that sealing a container of liquid hydrogen and letting it boil will increase its pressure to “over 140 Megapascals (20,000 psi).”